Vibrator support structure and manufacturing method for the support structure

ABSTRACT

In a vibrator support structure, a vibrator is supported on a substrate through support pins, substrate connection portions of the support pins and pin connection portions of the substrate are joined through conductive adhesive which is made of a resin including conductive filler and has a pencil hardness of about 4H or less, and the conductive adhesive has a thickness which can buffer vibrations and impacts propagated through the support pins.

This application is a Divisional Application of U.S. patent applicationSer. No. 10/735,704 filed Dec. 16, 2003, currently pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vibrator support structure and to amethod of manufacturing the support structure.

2. Description of the Related Art

Up to now, in vibrating gyroscopes, a vibrator support structureprovided with a vibrator having a bending vibration mode, support pinsfor supporting the vibrator, and a substrate on which the vibrator ismounted through the support pins has been adopted. That is, in thevibrator, a pair of piezoelectric substrates oppositely polarized in thethickness direction are joined so as to face each other, and onepiezoelectric substrate, on which first and second detector electrodesare formed so as to be separated from each other, and the otherpiezoelectric substrate, on the entire surface of which a driveelectrode is formed, are joined so as to sandwich an intermediateelectrode.

Then, the support pins are attached to the first and second detectorelectrodes at locations corresponding to vibration nodal points and alsothe support pins are attached to the drive electrode at locationscorresponding to vibration nodal points. Furthermore, a substrateconnection portion, which is an outer end portion of each support pin,is joined to each pin connection portion provided on the substrate bysoldering. Accordingly, the vibrator is mounted on the substrate throughthe support pins and is supported so as to be able to perform bendingvibration (see Japanese Unexamined Patent Application Publication No.2001-227953, for example).

Moreover, in another vibrator support structure, a substrate connectionportion, which is an outer end portion of an L-shaped support pin, isinserted into a through-hole of an attachment part which is not thesubstrate, and the substrate connection portion of the support pin isfixed to the attachment part by soldering. In this support structure, aseparate buffer material is placed between the attachment part and thesubstrate (see Japanese Unexamined Patent Application Publication No.6-221854 and Japanese Unexamined Patent Application Publication No.6-258082, for example).

In the vibrator support structures of the related art, the substrateconnection portion of the support pins and the pin connection portion ofthe substrate are joined by soldering. However, since the solder, whichis a metal, is solidified and hardens, vibrations leaking from thevibrator are easily propagated to the substrate through the support pinsand a residual stress is easily caused in the support pins. Furthermore,in such a support structure, it becomes easy for impacts applied to thesubstrate from the outside to be directly propagated to the vibratorthrough the support pins.

On the other hand, in a vibrator support structure in which anattachment part fixed on a substrate with a buffer material therebetweenand a substrate connection portion of a support pin are soldered, thereis an advantage in that the vibrations and impacts propagated throughthe support pin are weakened by the buffer material. However, the factis that, since it is necessary to place a buffer material between theattachment part and the substrate, the number of parts increases and thestructure becomes complicated, and, as a result, this requiresadditional during the assembling process.

Moreover, as long as a vibrator support structure using soldering isadopted, reflow mounting of a vibrating gyroscope accompanied by there-melting of solder cannot be avoided. Accordingly, the trouble ofchanging the balance between parts in the vibrator support structure,that is, damage of support conditions due to the release of residualstress, etc., is likely to occur.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a vibrator support structure in whichvibrations and impacts propagated through support pins are buffered, andalso provide a method of manufacturing such a novel vibrator supportstructure.

A vibrator support structure according to a first preferred embodimentof the present invention includes a vibrator, a substrate, and supportpins. In the support structure of a vibrator, the vibrator is supportedon the substrate through the support pins, substrate connection portionsof the support pins and pin connection portions of the substrate arejoined through a conductive adhesive which is made of resin including aconductive filler and has a pencil hardness of about 4H or less, and theconductive adhesive has a thickness which can buffer vibrations andimpacts propagated through the support pins. Accordingly, thepropagation of a vibration leaking from the vibrator to the substratethrough the support pins and the propagation of impacts applied to thevibrator from the outside through the support pins are effectivelysuppressed. Therefore, without providing any separate buffer material,the occurrence of residual stress to the support pins and damage of thevibrator can be prevented. Furthermore, when constructed in this way,variations in height (co-planarity) of the support pins can becompensated for.

In a vibrator support structure of preferred embodiments of the presentinvention, an opening allowing conductive adhesive existing between thevibrator connection portion of the support pins and the vibrator to oozeout is provided in the vibrator connection portion of the support pins.

In a vibrator support structure of preferred embodiments of the presentinvention, an opening allowing conductive adhesive existing between thesubstrate connection portion of the support pins and the pin connectionportion of the substrate to ooze out is provided in the substrateconnection portion of the support pins. When the opening is provided,since the contacting area between the conductive adhesive and thesupport pins increases, the vibrator connection portion of the supportpins and the vibrator or the substrate connection portion of the supportpins and the pin connection portion of the substrate can be morestrongly joined.

A method of manufacturing a vibrator support structure according toanother preferred embodiment of the present invention includes the stepof hardening conductive adhesive for joining the substrate connectionportion of the support pins and the pin connection portion of thesubstrate, the conductive adhesive existing therebetween, while only theweight of the vibrator and the support pins is applied. Accordingly, noresidual stress occurs in the support pins after the conductive adhesivehas been hardened and a sufficient thickness of the conductive adhesivecan be obtained to buffer vibrations and impacts.

A manufacturing method for a vibrator support structure of variouspreferred embodiments of the present invention preferably furtherincludes the step of coating each of the substrate connection portionand the pin connection portion with conductive adhesive in advance forjoining the substrate connection portion of the support pins and the pinconnection portion of the substrate. Accordingly, a sufficient quantityof conductive adhesive can be placed between the substrate connectionportion and the pin connection portion. Therefore, it becomes possibleto arrange the conductive adhesive to effectively buffer vibrations andimpacts.

Other features, elements, characteristics, steps and advantages of thepresent invention will become more apparent form the following detaileddescription of preferred embodiments with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing the assembled state of a vibrator supportstructure of according to a preferred embodiment of the presentinvention;

FIG. 2 is a perspective view showing the disassembled state of thevibrator support structure according to a preferred embodiment of thepresent invention;

FIG. 3 is an expanded perspective view showing support pins according toa preferred embodiment of the present invention;

FIG. 4 shows the temperature characteristics of drift of a vibratinggyroscope in which the vibrator support structure according to apreferred embodiment of the present invention is adopted; and

FIG. 5 shows the temperature characteristics of drift of a vibratinggyroscope in which the vibrator support structure according to apreferred embodiment of the present invention is adopted after thevibrating gyroscope has been reflow-mounted.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a side view showing the assembled state of a vibrator supportstructure according to a preferred embodiment of the present invention,FIG. 2 is a perspective view showing the disassembled state of thevibrator support structure according to the present preferredembodiment, and FIG. 3 is an expanded perspective view showing supportpins according to the present preferred embodiment. FIGS. 4 and 5 showtemperature characteristics of drift of vibrating gyroscopes. Thetemperature characteristics of drift means the change in output at restwhile no angular velocity is applied, that is, the change in outputversus temperature at rest. Moreover, in FIGS. 4 and 5, the verticalaxis represents output (V) at rest and the horizontal axis representstemperature (° C.).

The vibrator support structure according to the present preferredembodiment is adopted in vibrating gyroscopes, etc., and, as shown inFIGS. 1 and 2, includes a vibrator 1 preferably in the form of asubstantially rectangular solid having a bending vibration mode, foursupport pins 2 and 3 for supporting the vibrator 1, and a substrate 4 onwhich the vibrator 1 is mounted through the support pins 2 and 3.Moreover, the support pins 2 and 3 are made of a thin metal plate andare bent into the shapes shown in FIGS. 2 and 3.

In the vibrator 1, a pair of piezoelectric substrates 5 and 6, which areoppositely polarized in the thickness direction, are joined together,and a drive electrode (not illustrated) is arranged on the entire outersurface of one piezoelectric substrate 5. On the outer surface of theother piezoelectric substrate 6, first and second detector electrodes(not illustrated), which are separate from each other, are formed, andthe inner surfaces of the piezoelectric substrates 5 and 6 are joined soas to sandwich an intermediate electrode (not illustrated).

Vibrator connection portions 2 a of the support pins 2 are joined tolocations corresponding to vibration nodal points of the drive electrodedisposed on the piezoelectric substrate 5 by using conductive adhesive,that is, a conductive adhesive made of resin containing a conductivefiller and having the same hardness as a pencil hardness ofapproximately 4H or less. Also, vibrator connection portions 3 a of thesupport pins 3 are joined to locations corresponding to vibration nodalpoints at the first and second detector electrodes disposed on thepiezoelectric substrate 6 using the conductive adhesive (notillustrated).

That is, the support pins 2 and 3 include the vibrator connectionportions 2 a and 3 a in the width direction of the vibrator 1, substrateconnection portions 2 b and 3 b facing the substrate 4, and connectionportions 2 c and 3 c which are extended in a direction so as to moveaway from the vibrator 1 and bent downward or upward after beingextended in the length direction of the vibrator 1 and bent downward.Moreover, SA2024 (product name) produced by Fujikura Kasei Co., Ltd. canbe given as a specific example of the conductive adhesive used in thepresent preferred embodiment.

In each of the vibrator connection portions 2 a and 3 a of the supportpins 2 and 3, an opening 7 such as a round hole, etc., which allows theconductive adhesive between the vibrator connection portions 2 a or 3 aand the vibrator 1 to ooze out is provided. So, the conductive adhesiveexisting between the vibrator conductor portions 2 a and 3 a of thesupport pins 2 and 3 and the vibrator 1 oozes out through each opening 7and runs to the outer surface of the vibrator connection portions 2 aand 3 a which do not face the vibrator 1 and hardens. As a result, thevibrator connection portions 2 a and 3 a of the support pins 2 and 3 andthe vibrator 1 are securely joined by the conductive adhesive whichcontinues to maintain a certain level of elasticity after the hardening.Moreover, the opening 7 is not limited to a round hole, but may be asquare hole, a cut groove, etc.

Furthermore, the substrate connection portions 2 b and 3 b, which areouter end portions of the support pins 2 and 3 for supporting thevibrator 1, are joined to the pin connection portions 4 a which arepositioned and formed on the mounting surface of the substrate 4 so asto correspond to the substrate connection portions 2 b and 3 b by usingconductive adhesive existing therebetween. At this time, the conductiveadhesive 8 for joining the substrate connection portions 2 b and 3 b ofthe support pins 2 and 3 to the pin connection portions 4 a of thesubstrate 4 has a thickness which can sufficiently buffer the vibrationsand impacts propagated through the support pins 2 and 3, that is, thethickness between the substrate connection portions 2 b and 3 b and thepin connection portions 4 a.

Moreover, although not illustrated, the substrate connection portions 2b and 3 b of the support pins 2 and 3 may be provided with the same typeof opening as the vibrator connection portions 2 a and 3 a. When such anopening is provided, since the conductive adhesive existing between thesubstrate connection portions 2 b and 3 b of the support pins 2 and 3and the pin connection portions 4 a of the substrate 4 oozes out throughthe opening, it becomes possible to securely join the substrateconnection portions 2 b and 3 b and the pin connection portions 4 a.

That is, when the above-described support structure, in which thevibrator 1 is mounted on the substrate 4 through the support pins 2 and3, is used in a vibrating gyroscope and a signal is input between eachof the detector electrodes and the drive electrode, the vibrator 1performs bending vibration in a direction which is substantiallyperpendicular to the surface where the drive electrode is formed.Furthermore, when a rotational force is applied to the vibrator 1, thevibration direction changes because of the Coriolis force and a signalcorresponding to the change of the vibration direction is output fromthe detector electrodes. Therefore, when the output signal is measured,a rotational angular velocity applied to the vibrator 1 can be detected.

On the other hand, when the support structure of the vibrator 1according to the present preferred embodiment is manufactured, thefollowing assembly process is preferably adopted. First of all, thevibrator connection portions 2 a and 3 a of the support pins 2 and 3 arejoined to the top and bottom surfaces, respectively, of the vibrator 1using conductive adhesive. Next, the substrate connection portions 2 band 3 b of the support pins 2 and 3 joined to the vibrator 1 are coatedwith a sufficient quantity of conductive adhesive 8. Then, the substrateconduction portions 2 b and 3 b of the support pins 2 and 3 coated withthe conductive adhesive 8 are positioned on the respective pinconnection portions 4 a of the substrate 4 and held.

After that, the conductive adhesive 8 existing between the substrateconnection portions 2 b and 3 b and the pin connection portions 4 a ishardened while only the weight of the vibrator 1 and support pins 2 and3 is applied. At this time, since no external force other than theheight of the vibrator 1 and the support pins 2 and 3 is applied to theconductive adhesive 8, the hardened conductive adhesive 8 has asufficient thickness for buffering vibrations and impacts propagatingthrough the support pins 2 and 3 and there is no residual stress left inthe support pins 2 and 3.

Accordingly, the propagation of vibrations leaking from the vibrator 1through the support pins 2 and 3 and the direct propagation of impactsapplied to the substrate 4 to the vibrator 1 through the support pins 2and 3 are suppressed by the conductive adhesive 8, which continues tomaintain sufficient elasticity after hardening. Moreover, in the presentpreferred embodiment, although preferably only the substrate connectionportions 2 b and 3 b of the support pins 2 and 3 are coated with theconductive adhesive 8, as shown in FIG. 2, each of the substrateconnection portions 2 b and 3 b and the pin connection portions 4 a maybe coated with half of the conductive adhesive 8 a and 8 b, and then, itbecomes possible to easily apply a sufficient quantity of the conductiveadhesive 8.

Now, although the support structure of the vibrator 1 is adopted in avibrating gyroscope, it is known that the stability of vibratinggyroscopes is judged by temperature characteristics of drift, and it isdesirable that, regarding the temperature characteristics of drift, theoutput at rest or stationary state be flat in the measurementtemperature range. So, the inventor of the present invention and othershave measured the temperature characteristics of drift of two vibratinggyroscopes in which the support structure of the vibrator 1 described inthe present preferred embodiment is used, and the result of themeasurement was obtained as shown in FIG. 4. That is, in the vibratinggyroscopes A and B which adopted the support structure according to thepresent preferred embodiment, it was discovered that the output at restis flat in the measurement temperature range and the support structureof the vibrator 1 is stable.

Furthermore, when a vibrating gyroscope is reflow-mounted, there was afear that the support structure of the vibrator 1 may become unstable,but, when the inventor of the present invention and others mademeasurements of the temperature characteristics of drift of thevibrating gyroscopes A and B after they were reflow-mounted, themeasurement results shown in FIG. 5 were obtained. According to thesemeasurement results, the temperature characteristics of drift were notdeteriorated by the reflow mounting, and, since the support structure ofthe vibrator 1 continued to be stable, the balance between the parts didnot change; that is, the support condition did not change by the releaseof residual stress, etc. Moreover, the support structure of the vibrator1 is applied to not only vibrating gyroscopes, but can also be appliedto other electronic components.

In Japanese Unexamined Patent Application Publication No. 2000-146593,it is disclosed that the leakage of vibration to the support pins fromthe vibrator can be prevented by connecting the vibrator and the supportpins through conductive adhesive. In this case, the conductive adhesivemainly acts as a buffer for the vibration, and it may be said that it isanalogous to the contraction of preferred embodiments of the presentinvention in that the conductive adhesive is utilized as a vibrationbuffer. However, when the pencil hardness is low, the increasedviscosity may prevent the vibrator from vibrating. Accordingly, when thevibrator and the support pins are joined, it becomes necessary to setthe lower limit of the pencil hardness so as not to prevent the vibratorfrom vibrating.

On the other hand, in the case of preferred embodiments of the presentinvention, the main portion of the vibration buffer is the support pinsand the connection portion between the support pins and the substrateconstitutes the remainder of the function of the vibration buffer.Therefore, the lower limit of the pencil hardness is not particularlydefined. That is, the present invention and the technology described inJapanese Unexamined Patent Application Publication No. 2000-146593 arenot the same.

The present invention is not limited to each of the above-describedpreferred embodiments, and various modifications are possible within therange described in the claims. An embodiment obtained by appropriatelycombining technical features disclosed in each of the differentpreferred embodiments is included in the technical scope of the presentinvention.

1. A method of manufacturing a vibrator support structure comprising thesteps of: providing a vibrator which is supported on a substrate throughsupport pins; and hardening conductive adhesive for joining a substrateconnection portion of the support pins and a pin connection portion ofthe substrate, the conductive adhesive existing therebetween, while onlythe weight of the vibrator and the support pins is applied.
 2. A methodof manufacturing a vibrator support structure as claimed in claim 1,further comprising the step of coating each of the substrate connectionportion and the pin connection portion with conductive adhesive inadvance for joining the substrate connection portion of the support pinsand the pin connection portion of the substrate.
 3. A method ofmanufacturing a vibrator support structure as claimed in claim 1,wherein the conductive adhesive is made of resin including a conductivefiller and has a pencil hardness of about 4H or less.
 4. A method ofmanufacturing a vibrator support structure as claimed in claim 1,wherein the conductive adhesive has a thickness that is sufficient tobuffer vibrations and impacts propagated through the support pins.